ESP health check validates connectivity before processing

An email worker that starts processing jobs before validating its ESP credentials discovers a misconfiguration only when the first real send fails in production — potentially after dozens of jobs have been dequeued, acknowledged, and logged as in-flight. A rotated API key, a wrong environment variable, or a network policy blocking outbound HTTPS to the ESP creates a failure that only surfaces under load. ISO-25010:2011 reliability.availability requires that faults are detected at startup rather than at runtime, where the blast radius is larger.

Add a pre-startup health check in workers/email.worker.ts that exits the process with a non-zero code if the ESP is unreachable:

async function startEmailWorker() {
  const healthy = await emailProvider.healthCheck()
  if (!healthy) {
    logger.fatal('ESP health check failed — not starting')
    process.exit(1)
  }
  logger.info('ESP connectivity verified — starting worker')
  const worker = new Worker('email', processEmailJob, { connection })
  worker.on('error', (err) => logger.error(err, 'Worker error'))
}

startEmailWorker().catch((err) => {
  logger.fatal(err, 'Failed to start email worker')
  process.exit(1)
})

Verify all configured ESP providers, not just the primary, before the worker accepts its first job.